What is Heterochromatinization?
heterochromatinization (uncountable) (biochemistry) The conversion of euchromatin into heterochromatin during the inactivation of the X chromosomes in the embryogenesis of mammalian females.
Why is it called heterochromatin?
Heterochromatin was so named because its chromosomal material (chromatin) stains more darkly throughout the cell cycle than most chromosomal material (euchromatin).
What are the two types of heterochromatin?
Heterochromatins are mainly of two types; constitutive heterochromatin and facultative heterochromatin. Constitutive heterochromatin is the stable form of heterochromatin, i.e. it does not loosen up to form euchromatin ❑ It contains repeated sequences of DNA called satellite DNA.
What is the role of heterochromatin?
Heterochromatin is a constituent of eukaryotic genomes with functions spanning from gene expression silencing to constraining DNA replication and repair. Inside the nucleus, heterochromatin segregates spatially from euchromatin and is localized preferentially toward the nuclear periphery and surrounding the nucleolus.
How heterochromatin is formed?
At centromeres, heterochromatin formation is directed by RNA interference (RNAi) a naturally occurring process in the nucleus of eukaryotic cells that silences gene expression (Figure 2). RNAi during heterochromatin formation is an important step in the assembly of chromosome segregation machinery at mitosis.
Where is euchromatin found?
Euchromatin exists in decondensed form and is found in the distal arms of the chromosome. It is usually dispersed all around the nucleus and is replicated throughout the S phase. Euchromatin is the transcriptionally active form of chromatin.
What is heterochromatin function?
Is heterochromatin open or closed?
The former is considered to be an open structure favorable for transcription and is gene rich, whereas the latter is considered to be in a closed structure that tends to be refractory for transcription and is gene poor.
What is heterochromatinization and how does it work?
One such potential mechanism is the heterochromatinization of chromatin within a region of the genome containing a gene sequence, inhibiting any further molecular interactions with that underlying gene sequence and effectively inactivating that gene.
Does heterochromatinization lead to DNA methylation?
Thus, it is possible that heterochromatinization is followed by DNA methylation, and the resulting silencing of the underlying gene is likely inherited by subsequent generations through this epigenetic mechanism.
What is facultative heterochromatin?
Facultative heterochromatin is the result of genes that are silenced through a mechanism such as histone deacetylation or Piwi-interacting RNA (piRNA) through RNAi. It is not repetitive and shares the compact structure of constitutive heterochromatin.
Is heterochromatin an effective target for evolution?
If evolution makes sense only in the context of the regulatory control of genes, we propose that heterochromatin, which is the main form of chromatin in higher eukaryotes, is positioned to be a deeply effective target for evolutionary change.